Usenet is not an organization, and no group or individual has authority over Usenet as a whole. No one controls which users receive newsgroup access or who can post articles. It's not publicly funded in any way, and it is also not an academic network.
It is, however, a worldwide discussion medium. It consists of a set of "newsgroups," or discussion groups, on topics ranging from the sublime (alt.metaphysics, rec.org.mensa) to the ridiculous (alt.tasteless.jokes, alt.tv.beavis-n-butthead.) Articles or messages are posted to the newsgroups by users with the appropriate software.
Netscape Navigator, for example, features newsgroup access through its "Window" pull-down menu (users click on "Netscape News" to be transported to the Usenet window.) Usenet traffic is carried over the Internet and also over other, more obscure networks such as UUCP (a protocol suite for sending data over point-to-point connections, typically using dial-up modems.)
Some newsgroups are "moderated," meaning the articles are first sent to a group moderator for approval before posting. But they're the exception -- the vast majority of newsgroups have no moderators.
Usenet was created in 1979 by graduate students at Duke University, and soon became widely used as a communications network for Unix programmers in the days before the Web's ubiquity.